Forming machine

ABSTRACT

A forming machine for forming a workpiece having a rotatably drivable gripping device. The gripping device comprises a first forming tool and a press-on tool adapted to press the workpiece in the direction of the first forming tool. The forming machine further comprises a second forming tool mounted at least substantially co-axially round the press-on tool. The second forming tool can be moved along the press-on tool.

BACKGROUND OF THE INVENTION

[0001] The invention relates to a forming machine having a rotatably drivable gripping device for gripping a workpiece, such as a plate of stock material. The gripping device has a forming tool and a press-on tool for pressing the workpiece in the direction of the forming tool.

[0002] A forming machine of this kind is known for example from EP-A-0 125 720. With such a forming machine, a workpiece is formed by gripping it between the forming tool and a press-on tool or loose head, and subsequently moving a forming roller in a path that corresponds to the shape of the forming tool. Thus a cylindrical, oval-cylindrical or conical body having a flat bottom can be obtained. For more complex shapes, for example, parts for exhaust systems or pulleys intended for use in the automobile industry, it is necessary to remove the workpiece and grip it in a second forming machine. Subsequently, a deformation in a second, substantially opposite direction is completed in the second forming machine.

[0003] With each subsequent deforming step in another direction the workpiece needs to be removed and be placed in a different forming machine. These operations take a great deal of time and frequently result in inaccuracies when a workpiece is gripped repeatedly. This may result in products exhibiting dimensional variations that fall outside the desired range of tolerances.

SUMMARY OF THE INVENTION

[0004] A forming machine for forming a workpiece has a rotatably drivable gripping device. The gripping device comprises a first forming tool and a press-on tool adapted to press the workpiece toward the first forming tool. The second forming tool is mounted at least substantially co-axially around the press-on tool. The second forming tool further can be moved along the press-on tool.

[0005] Another aspect of the present invention is a method for forming a workpiece. The method includes gripping the workpiece between a first forming tool and a pressing tool. After gripping the workpiece, the workpiece is deformed on the first forming tool by moving a forming roller in a path that corresponds to the shape of a first forming tool. After deforming on the first forming tool, the workpiece is further deformed on a second forming tool on a side of the workpiece remote or opposite from the first forming tool by moving a forming roller in a path that corresponds to the shape of the second forming tool.

[0006] In other words, a forming machine has a second forming tool, which is mounted at least substantially co-axially around a loose head, which second forming tool can be moved along the press-on tool or the loose head.

[0007] Once a workpiece is fixed by gripping, this second forming tool is located on the side of said workpiece remote from the first forming tool. By pressing the second forming tool against the workpiece after a first deformation of the workpiece on the first forming tool, and changing the axial position of said second forming tool with respect to the loose head, the workpiece can be deformed by means of a forming roller in the direction of the second forming tool. The workpiece need not be removed thereby, as a result of which the time-consuming removing and renewed gripping of the workpiece is no longer required and, in addition, shifting of the workpiece cannot take place.

[0008] If the shape of the workpiece makes it necessary to reverse the direction of deformation i times (i= 1, 2, 3, . . . ), it is possible to provide i additional forming tools. Thus it is possible to mount a third forming tool co-axially round the first forming tool, which third forming tool can be moved along the first forming tool.

[0009] An effective way of ensuring that the additional forming tools cannot rotate with respect to the forming tool or the loose head on which they are mounted, whereas translating movement is possible, is for example the use of key-ways. Key-ways are easy to make, they allow translating movement and they ensure an effective transmission of forces and torques between the parts that are fitted together.

[0010] In principle, the forming machine according to the invention can be fitted with a single, preferably symmetrical forming roller, which can be moved to the other side of the workpiece with each subsequent deforming step.

[0011] The invention furthermore relates to a method for forming a product, wherein a workpiece, for example a plate of stock material, is gripped between a first forming tool and a press-on tool or loose head, and is deformed on the first rotary forming tool by moving a forming roller in a path that corresponds to the shape of the first forming tool. The method is characterised in that subsequently a second forming tool is placed in abutment with the workpiece, on the side remote from the first forming tool, and that the workpiece is deformed on the second rotary forming tool by moving a forming roller in a path that corresponds to the shape of the second forming tool.

[0012] The invention will be explained in more detail hereafter with reference to the drawings, which show exemplary embodiments of the forming machine according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a schematic top plan view of a forming machine according to the present invention.

[0014]FIG. 2 is a partial schematic sectional view of the gripping device of the forming machine according to FIG. 1.

[0015] FIGS. 3A-3F schematically show steps of an exemplary method according to the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0016]FIG. 1 schematically shows a top plan view of a forming machine 1 according to the invention, which comprises a rotatably drivable gripping device 2. Gripping device 2 comprises a first forming tool or chuck 3 and a press-on tool or loose head 4, which are mounted co-axially in such a manner as to be capable of rotating movement. Forming tool 3 can be driven by an electric motor or other suitable means(not shown).

[0017] A workpiece, for example a disc-shaped metal plate as shown in FIGS. 2-3F, can be gripped between the first forming tool and the loose head 4 in a manner that is known. The a metal plate may for example have a thickness ranging from 1-12 mm and a diameter of 200-700 mm. The metal plate can be formed into a desired product forming roller 5, which is rotatably mounted in a holder 6. Holder 6 is supported by a movable Y-slide or upper slide 7, which is mounted on a movable X-slide or lower slide 8 as is commonly known. Lower slide 8 is translatably mounted on machine bed 9 of the forming machine 1. Slides 7, 8 and their respective driving slides are accommodated in a housing. Since these parts are not essential for the present invention, reference is made to Dutch patent application no. 1000851 and to European patent application no. 0 125 720 for a more detailed explanation, the contents of which are hereby incorporated by reference.

[0018] The forming machine furthermore comprises a control unit 10. The control unit 10 may include an input device, a display screen and a memory. The shape of forming tool 3 is stored in the memory of control unit 10 with a view to forming the metal plate on chuck 3 in the production stage. The path followed by forming roller 5 is then determined by taking into account the thickness of the metal plate, for example as disclosed in applicant's Dutch patent application no. 1001675, the content of which is hereby incorporated by reference.

[0019]FIG. 2 shows the gripping device 2 of the forming machine 1 in more detail. Forming tool 3 is circular in section, with the diameter varying in axial direction. An end 11 of forming tool 3 has the smallest diameter, which gradually increases in axial direction, so that a frustoconical shape is obtained. From there the diameter of forming tool 3 then increases and subsequently remains constant along the remaining length of forming tool 3.

[0020] Positioned opposite forming tool 3 is loose head 4, which comprises a cylindrical pre-bearing shaft 12 and a conical press-on disc 13. The diameter at the end of press-on disc 13 is identical to the diameter at the end 11 of forming tool 3. Pre-bearing shaft 12 is supported in a first group of bearings 14 and a second group of bearings 15, with said second group of bearings 15 being mounted around a hollow cylindrical part 16. The hollow cylindrical part 16 is mounted on pre-bearing shaft 12 (by means of keyways not shown). Hollow cylindrical part 16 furthermore comprises a flange 17, to which a second forming tool 18 is fixed. When second forming tool 18 is connected to the pre-bearing shaft 12 in this manner, there is no need to provide additional bearings for second forming tool 18.

[0021] After a workpiece, in this example a disc-shaped metal plate 19, has been gripped between first forming tool 3 and loose head 4, the workpiece is worked in a first processing step so that it conforms to the shape of end 11 of first forming tool 3. The second forming tool 18 is placed in abutment with the deformed disc-shaped metal plate 19. Here the shape of second forming tool 18 is at least partially complementary to the shape of first forming tool 3 so that second forming tool 18 is capable of accommodating the end 11 of first forming tool 3 and the deformed disc-shaped metal plate 19. The second forming tool 18 also contributes to the gripping force exerted on the deformed disc-shaped metal plate 19.

[0022] Mounted around first forming tool 3 is a third forming tool 20 by means of key-ways, for example. The shape of third forming tool 20 is partially complementary to that of second forming tool 18, so that said third forming tool 20 is capable of accommodating part of second forming tool 18 and the deformed disc-shaped metal plate 19. Third forming tool 20 also clamps deformed disc-shaped metal plate 19 against second forming tool 18.

[0023] FIGS. 3A-3F schematically illustrate a method for forming a product, in this case, again a disc-shaped metal plate 21. The gripping device as shown corresponds largely to the gripping device shown in FIG. 2.

[0024] Before the deforming operation is started, disc-shaped metal plate 21 is clamped between conical end 22 of first forming tool 23 and end 24 of a loose head 25. The forming machine used comprises a holder 26, on which a first forming roller 27 and a second forming roller 28 are rotatably mounted. Holder 26 is symmetrical in shape, and forming rollers 27 and 28 are mounted in mirror symmetry with respect to the plane of symmetry of holder 26. Those skilled in the art will appreciate it is also possible to use one forming roller or a tool exchanger fitted with 2 to 5 forming rollers. Once the workpiece is gripped, the first forming tool 23 is driven, generally at a number of revolutions ranging between 500 (for plates having a large diameter) and 2400 (for plates having a small diameter). The loose head 25 is driven by workpiece 21.

[0025] The first forming roller 27 is placed in abutment with the workpiece 21 at the location of the point of contact of the end 24 of loose head 25, and then is moved in a path that corresponds to the shape of first forming tool 23. After workpiece 21 has taken on the shape of the end 22 of forming tool 23, first forming roller 27 is removed from workpiece 21 and holder 26 is moved to the other side or rear side of workpiece 21.

[0026] Then, a second forming tool 29 is placed in abutment with workpiece 21, and second forming roller 28 is moved into contact with the other side of workpiece 21. Then, the forming roller 28 is moved in a path that corresponds to the shape of second forming tool 29, and after the second deforming step is complete the second forming roller 28 is moved away from workpiece 21 and holder 26 is moved to the other side of workpiece 21.

[0027] A third forming tool 30 is moved into contact with the rear side of workpiece 21, while the first forming roller 27 is moved into contact with the front side of workpiece 21. Then, the first forming roller 27 is moved in a path that corresponds to the shape of third forming tool 30. Following this, the workpiece 21 can be removed from the gripping device by moving the second forming tool 29 and the third forming tool 30 and the loose head 25 away from the workpiece 21.

[0028] The forming machine and the method according to the present invention make it possible to form a workpiece in two substantially opposite directions without a need to remove the workpiece from the forming machine. This makes it possible to reduce production times and avoid inaccuracies that may occur when re-gripping of the workpiece is necessary.

[0029] It is noted that the forming tools do not necessarily have to be of circular section. Thus it is possible, for example, for the first forming tool to have a circular section, while the second forming tool has an oval outer circumference that corresponds to the outer circumference of the second forming tool, while the outer circumference of the third forming tool is circular again.

[0030] The forming machine and the method according to the present invention are suitable for manufacturing shells for use in exhaust systems of e.g. trucks.

[0031] The present invention is not restricted to the above-described embodiments, which can be varied in several ways within the framework of the claims. The gripping device may also be positioned vertically (rotatable about a vertical axis). This arrangement facilitates horizontal transport and positioning upon subsequent processing steps of the workpieces, which has significant advantages in mass production. 

What is claimed is:
 1. A forming machine for forming a workpiece comprising: a rotatably drivable gripping device, the gripping device comprising a first forming tool and a press-on tool adapted to press the workpiece toward the first forming tool; a second forming tool mounted at least substantially co-axially around the press-on tool, wherein the second forming tool can be moved along the press-on tool.
 2. The forming machine according to claim 1 and further comprising a third forming tool mounted co-axially around the first forming tool, wherein the third forming tool can be moved along the first forming tool.
 3. The forming machine according to claim 1 , wherein at least one of the second forming tool, the press-on tool and the third forming tool is movably mounted on the first forming tool.
 4. The forming machine according to claim 3 , wherein the shape of said second and/or said third forming tool is at least partially complementary to the shape of the first and/or a second forming tool, respectively, complemented with the local thickness of the workpiece.
 5. The forming machine according to claim 1 and further comprising two forming rollers.
 6. the forming machine according to claim 5 , wherein the forming rollers are mounted on a single holder.
 7. A method for forming a workpiece comprising: gripping the workpiece between a first forming tool and a press-on tool; deforming the workpiece on the first forming tool by moving a forming roller in a path that corresponds to the shape of the first forming tool; and deforming the workpiece on a second forming tool on side the workpiece remote from the first forming tool by moving a forming roller in a path that corresponds to the shape of the second forming tool.
 8. The method according to claim 7 and further comprising deforming the workpiece on a third forming tool by moving a forming roller in a path that corresponds to the shape of the third forming tool.
 9. An exhaust system or a supply comprising a hollow product having a specific wall thickness, which has been obtained by means of the method according to claim 7 .
 10. A forming machine for forming a workpiece comprising: a rotatably drivable gripping device, the gripping device having a first forming tool and a press-on tool adapted to press the workpiece toward the first forming tool in a first direction; and means for deforming the workpiece in a second direction substantially opposite from the first direction. 